1. Field of the Invention
The present invention relates to a lens barrel and an imaging apparatus.
2. Description of the Related Art
There has been proposed a lens barrel including a zoom mechanism that moves a plurality of lenses to a predetermined position by causing a linear cylinder to restrict the movement of a plurality of lens holding frames in the rotational direction while moving the plurality of lens holding frames for holding the plurality of lenses, respectively, in the optical axis direction by the rotation of a cam cylinder.
In order to meet the recent requirement for increasing an image-taking magnification, the number of lenses increases and a total extended length increases, resulting in a tendency with an increase in size of a lens barrel. On the other hand, there is also a requirement for thinning of a camera, and thus, the thickness of the camera when the lens barrel is retracted into the camera body needs to be reduced as much as possible.
In order to achieve thinning of a camera, it is contemplated that barrels of which the dimension is reduced in the optical axis direction are connected in a multi-stage configuration. However, there are many restrictions for disposing a plurality of cam grooves on a barrel without mutual intersection in terms of space.
Thus, Japanese Patent Laid-Open No. 2006-65138 discloses a lens barrel of which a total extended length can be increased by forming a gear disposed on the outer circumferential surface of a cam cylinder in a stepwise shape.
However, in the lens barrel disclosed in Japanese Patent Laid-Open No. 2006-65138, a total extended length can be increased only by the amount of movement of the stepwisely-moved gear. In addition, the gear needs to be disposed on the outer circumference side of the flange portion of a linear cylinder, and the length of the cam cylinder is also increased by the amount of movement of the gear, resulting in a difficulty in reduction in diameter of the barrel and thinning thereof.